As is generally known, an electric generator such as an alternator and/or a generator, and an electromotor (hereinafter, referred to as an “electric machine”) such as a motor and/or a linear motor may be configured with a stator and a rotor configured to relatively move with respect to the stator.
The stator of the electric machine may be configured with a stator core having a plurality of slots, and stator windings wound around the slots.
The stator windings may be typically configured by a method of winding a wire (stranded wire) having a relatively thin diameter around an internal portion of the slot a multiple number of times and a method of winding a wire around the tooth (pole) in a concentrated manner.
However, in this type of stator winding method in the related art, the operation efficiency may be reduced because a ratio of an occupied area (cross-sectional area) of the conductor (coil) with respect to a cross-sectional area of the slot is relatively small. Furthermore, there is a limit in increasing a cross-sectional area ratio of the conductor with a conventional stator winding method using a wire having such a thin diameter, thereby limiting the enhancement of the output density and efficiency.
But for an electromotor for electric vehicles requiring a high output density and high efficiency, it may be very important to increase a ratio of a cross-sectional area of the conductor with respect to the slot.
Considering such problems, there are known methods of inserting a rectangular copper wire having a relatively large width (diameter) into a slot to form a stator winding (for example, U.S. Published Patent Application No. 2003/0214196, filed May 15, 2003).
However, even using a rectangular copper wire, there is a problem in which the size of the stator and rotor in an electromotor should be increased to enhance the output of the electromotor.
And with a conventional stator winding method using a rectangular copper wire, it is not easy to control the number of turns, thus resulting in a limit on the high-speed operation (for example, above 7000 rpm (revolution per minute).